Tumor shape as a prognostic factor for the growth of intracanalicular vestibular schwannoma: a long-term observational study.

Objective: To evaluate the predictive factors of tumor growth in patients with vestibular schwannoma (VS) managed with the wait-and-scan approach.

Methods: The data of 31 patients diagnosed with intracanalicular VS and followed for > 5 years were retrospectively analyzed. VS was diagnosed according to MRI findings and tumor growth was monitored. Tumor growth was defined as an increase of 2 mm or more in the maximal tumor diameter. The association between the initial tumor size and shape and tumor growth was assessed.

Results: Tumor growth was observed in 16 of 31 patients (51.6%) over a mean follow-up duration of 7.3 years. The initial tumor size was not statistically correlated with tumor growth. However, fusiform or cylindrical tumors exhibited higher growth rates than oval or round tumors. Additionally, a significant correlation was observed between cerebellopontine angle extension and tumor shape.

Conclusions: In this study, 51.6% of the patients with intracanalicular VS who were managed with the wait-and-scan strategy over a follow-up period of > 5 years showed tumor growth. Tumor shape, especially fusiform or cylindrical shape, was found to be a significant predictor of tumor growth.